Land use effects on plant communities in urban ecosystems

The spatial configuration of urban landscapes, characterized by complex mosaics of fragmented patches subjected to different land uses, shapes biodiversity and, therefore, affects ecosystem stability and functioning. The present study, carried out in the context of the PNRR MUR “National Centers” Member – CN_00000033 “National Biodiversity Future Center - NBFC”, focuses on evaluating the effects of land use and fragmentation on the biodiversity of the herbaceous vegetation in urban contexts. Specifically, the structural and functional biodiversity was analysed, within the area of the University of Salerno (Southern Italy), along gradients of increasing distance from interfaces between different land use patches, such as pathways, lawns and tree rows. Taxa were identified at the species level, estimating their abundance through measures of number, dry mass and Braun- Blanquet cover, and functional traits, such as the biological form, chorological type and Ellenberg indices, were adopted in evaluating vegetation functional diversity. Data analysis relied on the derivation of synthetic structural and functional diversity indices, employed together with community composition and species abundances in ascertaining how land use and the margin effects drive the diversity of plant communities. Overall, results show that land use differentially affects the structural and functional biodiversity of plant communities, both varying also in relation to the margin effect, even at scales in the order of few meters. Main drivers related to land use appear to be tree canopy shading and trampling/soil sealing, determining an abundance of terophytes in open and trampled spaces and a proportional increase in hemicryptophytes and chamaephytes under deciduous canopies. The association of several species to specific tree canopies may also explain changes in the chorological composition of communities and alterations in their dominance-diversity structures. Moving forward from the estimation of impacts to a proactive stance, our findings may also contribute to develop more sustainable urban planning approaches.